For LoRaWAN devices, you must have a network-server in your infrastructure, which will handle the de-duplication, LoRaWAN mac-layer and forward the application payloads to an application-server. In case of the LoRa Server project, this is the LoRa App Server component which integrates with MQTT.

Yes, when your device has a direct internet connection I don’t see a reason why that should not work. Anyway, that is totally unrelated to the LoRa Server project which deals with the LoRaWAN protocol, so this forum is not the right place to discuss this.